package main

import (
	"fmt"
	"os"
	"path/filepath"
	"syscall"
	"unsafe"
)

var dll *syscall.LazyDLL

func main() {
	dllPath := resolveDLLPath()
	dll = syscall.NewLazyDLL(dllPath)
	if err := dll.Load(); err != nil {
		fmt.Fprintf(os.Stderr, "load %s failed: %v\n", dllPath, err)
		os.Exit(1)
	}

	usbNames := enumPortNames("Port_EnumUSB")
	fmt.Printf("USB: %v\n", usbNames)

	prnNames := enumPortNames("Port_EnumPRN")
	fmt.Printf("PRN: %v\n", prnNames)

	data := []byte{0x1B, 0x40, 0x1B, 0x7B, 0x00, 'T', 'E', 'S', 'T', '\n', '\n', '\n', 0x1B, 0x69}
	if len(os.Args) >= 3 {
		fileData, err := os.ReadFile(os.Args[2])
		if err != nil {
			fmt.Fprintf(os.Stderr, "read %s failed: %v\n", os.Args[2], err)
			os.Exit(1)
		}
		if !tryOpenPrint(os.Args[1], fileData) {
			os.Exit(1)
		}
		return
	}
	if len(os.Args) == 2 {
		if !tryOpenPrint(os.Args[1], data) {
			os.Exit(1)
		}
		return
	}

	for _, name := range prnNames {
		fmt.Printf("Trying PRN: %s\n", name)
		tryPrint(name, data)
	}
	for _, name := range usbNames {
		fmt.Printf("Trying USB: %s\n", name)
		tryOpenPrint(name, data)
	}
}

func resolveDLLPath() string {
	if exe, err := os.Executable(); err == nil {
		localPath := filepath.Join(filepath.Dir(exe), "CsnPrinterLibs.dll")
		if _, err := os.Stat(localPath); err == nil {
			return localPath
		}
	}
	return "CsnPrinterLibs.dll"
}

func enumPortNames(procName string) []string {
	var buf [256]byte
	ret, _, _ := dll.NewProc(procName).Call(uintptr(unsafe.Pointer(&buf[0])), uintptr(len(buf)))
	if ret == 0 {
		return nil
	}
	var names []string
	for start := 0; start < len(buf); {
		end := start
		for end < len(buf) && buf[end] != 0 {
			end++
		}
		if end == start {
			break
		}
		names = append(names, string(buf[start:end]))
		start = end + 1
	}
	return names
}

func tryPrint(name string, data []byte) bool {
	nameB := append([]byte(name), 0)
	h, _, _ := dll.NewProc("Port_OpenPRNIO").Call(uintptr(unsafe.Pointer(&nameB[0])))
	if h == 0 {
		fmt.Printf("  OpenPRN failed\n")
		return false
	}
	defer dll.NewProc("Port_ClosePort").Call(h)
	dll.NewProc("Port_SetPort").Call(h)
	w, _, _ := dll.NewProc("WriteData").Call(uintptr(unsafe.Pointer(&data[0])), uintptr(len(data)), 3000)
	fmt.Printf("  WriteData: %d bytes\n", w)
	return int(w) == len(data)
}

func tryOpenPrint(name string, data []byte) bool {
	nameB := append([]byte(name), 0)
	h, _, _ := dll.NewProc("Port_OpenUSBIO").Call(uintptr(unsafe.Pointer(&nameB[0])))
	if h == 0 {
		fmt.Printf("  OpenUSB(%s) failed\n", name)
		return false
	}
	defer dll.NewProc("Port_ClosePort").Call(h)
	dll.NewProc("Port_SetPort").Call(h)
	w, _, _ := dll.NewProc("WriteData").Call(uintptr(unsafe.Pointer(&data[0])), uintptr(len(data)), 3000)
	fmt.Printf("  USB WriteData: %d bytes\n", w)
	return int(w) == len(data)
}